Did this during the summer. 
It is intended as a prototype - to prove that I could control motors with the Arduino with my software. This was DC motors with a feedback switch (motion, not position). Not shown on the videos is that fact that the Serial IO is done non-blocking (doing my own buffering) and there is an additional temperature monitoring (not used here).
The mechnics is not as good as might be done with Fischertechnik. I've got a slack in the way the pen is held so it may be off by ½cm before it draws. Also a minor bug, the carriage may move before the pen has reched the up or down position. (Fixed that later, didnt do a new video). I also rebuild the model, but couldnt get the pen mechanics much better. This is my Fischertechnic from 40 years ago.
The software on the laptop is in Delphi V5 which communicates to the Arduino, there is XOn/Off flow control, and it can take keyboard entry or spool a file with coordinates (a limited set of GCode commands)
Ah, yes, almost forgot 
- the links:
